ABB RELION REX640 - Page 1740

An example of the feature is shown in Figure 927 where the initial coil position
is at 60 A, the parallel resistor is disconnected and the target position is at 110
A. Before the controller starts moving the coil, it estimates if the zero-sequence
voltage at target position is below the V Res maximum setting and if the movement
is allowed. If the conditions allow, the controller starts moving the coil towards the
higher current. While the movement stops at V Res maximum (set to 3.5 percent
of the system's nominal phase-to-earth voltage in this example), the controller
automatically connects the parallel resistor and moves the coil to the desired
inductive current position (that is, 110 A). After the coil has reached the target
position, the controller automatically disconnects the resistor, that is, returns it to
its original connection state while simultaneously obtaining the target position of
110 A with the parallel resistor disconnected.
20 40 60 80 100 120 140
Coil inducve current [A]
Uo [%]
1
1.5
2.0
2.5
3.0
3.5
4.0
4.5
V Res maximum
Resistor OFF
Resistor ON
Inial posion = 60A
Target posion =
110A
Figure 927: Damping of the resonance curve by using the parallel resistor
The number of maximum tuning cycles can be limited with Tuning cycles setting.
The delay between consecutive tuning cycles is controllable by setting Tuning cycles
delay . After the maximum number of tuning cycles is reached, the tuning procedure
can be started by activating the ST_TUNING input, for example, via HMI application.
The counter for maximum tuning cycles is reset after a successful tuning operation.
The ALARM output is a general problem indication during the tuning process.
Usually, it is an indication of not obtaining a required minimum level or change
of zero-sequence voltage during the coil movement. The reason for this might be,
for example, a very symmetrical network. Other reasons for the ALARM indication
are coil movement into wrong direction, maximum number of tuning sequences
exceeded or simultaneous indication from both end switches of the coil. There is a
dedicated MOT_ALARM output indicating no detected coil movement after activating
RAISE_OWN or LOWER_OWN outputs.
After ALARM indication with ALARM_STS “Umin not reached” or “Cannot obtain
minimum Uo variation” the coil is moved to a position which is defined with
Error
Control functions
1MRS759142 F
1740 REX640
Technical Manual